Western Olivaceous Warbler

Iduna opaca

Order: Passeriformes
Family: Acrocephalidae
Presence in the Strait: Seasonal
Abundance: scarce
IUCN (global): LC · Least concern
In Spanish: Zarcero bereber

Photograph: Ron Knight, CC BY, vía iNaturalist

Length: 13 cm
Weight: 10 g

Presence in the Strait

Scarce summer visitor to scrub and woodlands close to watercourses. The subspecies found in the Iberian Peninsula and NW Africa is H. p. opaca.

Identification

Easy to confuse with a Reed Warbler but grey-brown upperparts and whitish underparts. Short pale supercilium, flat forehead with long broad-based bill and grey-brown legs.

Movements

Prenuptial peak in 2nd hf. May and postnuptial in 2nd hf. August and 1st hf. September.

Bioestrecho editorial text. Last revised: 8 September 2026.

Photographs from iNaturalist observations with the licence checked file by file. Those marked “Strait” were taken within the area; place and date are those of each observation.

Calendar in the Strait

21 %

Peak in May. Observations under CC0 or CC BY licences. The distribution also reflects observation effort.

Where it is seen

Open records from the atlas database, in cells of about 3.6 km. Opacity follows the square root of the count, and also reflects where people observe most.

See on the map

First open record: 2 May 1972
Latest record: 27 September 2024

The oldest and the most recent open observation in the extended area. A recent first observation does not mean the species is new: it means nobody had published it openly before.

Conservation

The catalogues, Andalusian and Spanish, are what binds; the Red Book assesses the Spanish population with IUCN criteria, and the global Red List is the context.

LCNTVUENCR

Andalusian Catalogue: Not included
Spanish Catalogue: Not included
Red Book of the Birds of Spain 2021: DD · Data deficient · breeding
Global Red List (IUCN): LC · Least concern

Andalusian Catalogue: Junta de Andalucía, list of 24 April 2025. Spanish Catalogue: MITECO, table of 30 June 2025. Red Book: SEO/BirdLife, 2021 (Annex I). IUCN: via GBIF, 6 September 2026. Red Book and IUCN categories are assessments; catalogue categories are legal obligations.

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Acrocephalidae
GBIF taxon key: 5739355

Sources

Distribution and calendar: Bioestrecho's own database, ingested from GBIF and OBIS
Photograph: Ron Knight, CC BY, vía iNaturalist
Taxonomy: GBIF backbone, pending WoRMS for marine taxa
Editorial text: written by Bioestrecho
Last revised: 8 September 2026

Western Olivaceous Warbler

Presence in the Strait

Identification

Movements

Gallery